A resin composition for sealing (which may be referred to as a sealant) generally contains a major component containing a polymer compound, such as organopolysiloxane, polyisobutylene with silyl end groups, a modified silicone polymer, a polysulfide polymer and the like, with a plasticizer, such as a phthalate ester, a process oil, polypropylene glycol and the like, a filler such as calcium carbonate and the like, and an additive, such as an antioxidant, a dripping preventing agent, a curing catalyst and the like, and the like. A sealant having such a formulation is used for assuring water tightness and air tightness by filling in a gap (joint) at a joint part or a contact part in such fields as construction, automobile, chemical industry and the like. In particular, it is used in a large amount for construction and used as a filler for an exterior wall.
However, a conventional resin composition for sealing involves tackiness (stickiness) remaining on the surface after curing, which may provide problems, such as damage on appearance due to dusts and sands easily attached thereto, deterioration of adhesiveness of a paint, and the like, and improvements are being demanded.
For solving the problems, there are proposals that a photocurable substance, such as a hydrolyzable silicon-containing polymer, an oligoester acrylate, a polyvinyl cinnamate compound and the like, is added to remove the surface tackiness (stickiness) (Patent Documents 1 and 2). However, the photocurable substance involves a problem of requiring a prolonged period of time until the function thereof is exhibited.
There is a proposal that a liquid diene polymer (such as polybutadiene or the like) is added to a hydrolyzable silicon-containing polymer (Patent Document 3). However, a liquid diene polymer has high viscosity, and when a large amount of a plasticizer is added thereto for ensuring workability, the plasticizer itself oozes on the surface (bleed-out) to cause stickiness.
Furthermore, there is a proposal of a one-component moisture-curable sealant containing (A) a urethane prepolymer with isocyanate end groups obtained by reacting an acryl polymer-containing polyol, which is obtained by polymerizing an alkyl acrylate ester in a polyoxyalkylene ether type polyol, with a polyisocyanate, and (B) a polyethylene glycol diester (Patent Document 4). However, the one-component moisture-curable sealant contains an acryl monomer that is not completely reacted to fail to solve the problem of stickiness, and also involves a problem in coating operation since the polyethylene glycol diester having high viscosity is contained.
There is a proposal of production of a urethane prepolymer by polymerizing an acrylic monomer in a polyol with a polymerization initiator having active hydrogen (Patent Document 5). However, the urethane prepolymer contains an acrylic monomer that is not completely reacted to fail to solve the problem of stickiness.
[Patent Document 1] JP-A-55-36241
[Patent Document 2] JP-A-5-65400
[Patent Document 3] JP-A-1-149851
[Patent Document 4] JP-A-11-50045
[Patent Document 5] JP-A-2001-115129